Examples of a method for treating a bulge such as an aneurysm formed in a blood vessel include a method in which an in-vivo indwelling member such as an embolus material is inserted into a bulge. By such a treatment, a thrombus can be formed around the embolus material within the bulge to reduce the risk of rupture of the bulge. To insert an embolus material into a desired bulge, first, a medical instrument called microcatheter which includes an elongated tube having a small diameter is inserted into a blood vessel and guided to the bulge such as an aneurysm. Then, the embolus material is inserted into the bulge through the inner cavity of the tube of the microcatheter and indwelled therein.
As such an embolus material, a material has been widely used which is prepared by shaping a metal wire into a coil shape to form a linear primary coil, followed by further shaping the linear primary coil into a helical shape to form a secondary coil. In guiding the embolus material to a bulge such as an aneurysm, the shape of the embolus material is made straight in the thin tube of the microcatheter. When the embolus material is released from the tube within the bulge, the shape returns to the original shape of the secondary coil, and the embolus material can remain within the bulge. A coil referred to as the secondary coil is obtained by imparting a secondary shape that is a three-dimensional shape to a linear primary coil.
Meanwhile, examples of the shape of a bulge include a spherical shape, an elliptical spherical shape, and a two-bulge shape, and a shape in which another blood vessel branches from a bulge. Among them, one of bulge types called a wide-neck aneurysm which has a wide boundary with respect to a parent blood vessel, relative to the diameter of the aneurysm, may cause a serious risk, as follows. AA helical secondary coil, for example, having a uniform diameter in the axial direction thereof may be used in indwelling a secondary coil within the bulge. The shape of the secondary coil to be used is cylindrical and does not sufficiently correspond to the shape of the inner wall surface of the bulge, and the neck opening is wide. With this, the pressing force of the secondary coil against the inner wall surface of the bulge is reduced, thereby avoiding the secondary coil from remaining within the bulge, even when the shape of the secondary coil returns to the original coil shape within the bulge. This causes the secondary coil to protrude to the parent blood vessel and to be flown to the periphery by the blood flow.
For such a wide-neck aneurysm, the secondary coil may have a shape that is not helical as described above but is a complicated three-dimensional structure, which is different from a helical shape, and partially fits the shape of the inner wall surface of the bulge. This allows the secondary coil to return to the three-dimensional structure within the bulge so as to apply pressing force to the inner wall surface of the bulge. Accordingly, the secondary coil is firmly fixed, resulting in a reduction in the possibility that the secondary coil protrudes to the parent blood vessel.
Regarding the secondary coil having such a complicated three-dimensional structure different from a helical shape, various production methods therefor have already been disclosed. For example, Patent Literature 1 discloses a method for producing a secondary coil having a three-dimensional structure by winding a primary coil around a core having a mandrel shape (with a pin), a clover shape, or a cubic shape. However, when the primary coil is wound around the core as described above to form a complicated three-dimensional structure in which the primary coil may be damaged upon being wound in the production process, it is necessary to pay attention to the order of winding of the primary coil. This causes the work to be complicated.
In addition, Patent Literature 2 also discloses a method for producing a secondary coil having a three-dimensional structure by winding a coil around a core, such as a rod, a cube, and a core with a groove. Similarly to the case of the method disclosed in Patent Literature 1, this method has problems in damaging a primary coil upon winding, and in workability.
Meanwhile, Patent Literature 3 discloses, in addition to a method in which a primary coil is wound around a core or the like, a method for producing a secondary coil having a spherical three-dimensional structure by inserting a primary coil into a spherical mold. In the method using a mold, a spherical internal space is formed by fitting together paired molds each having a hemispherical internal space, and a secondary coil having a spherical three-dimensional structure is formed by inserting a primary coil into the internal space. However, this method has the following problem. As shown in FIG. 27, it is easy to insert a primary coil 1 into an internal space 201 of a mold 200, but movement of the primary coil 1 in the internal space 201 cannot be controlled. Thus, the primary coil 1 is not inserted in a random manner and is made into a general helical shape. In addition, with the general helical shape, the primary coil cannot be arranged in the internal space 201 as intended, and therefore uniform secondary coils cannot be stably shaped.